Why did my fiddlestics ficus leaf turn brown & leaves are falling off?

Where is it plant in a pot or the ground?Sounds like you may be overwatering.If in a pot,did you ever re-pot in fresh soil?

If, it's in a pot, yes maybe overwatering it possibly. Especially if there are no drainage holes or maybe not enough

Also, has it recently been moved from one site to another? Sometimes they are unhappy with the change, whether because of change in amount of sunshine or exposed to a possible draft.

The only time my now 25 year-old ficus loses its leaves is if it hasn't been watered once a week. If I somehow get distracted and leave it for say, ten or so days, it drops its leaves. It has been moved many, many times - spending many hours in either a hot moving van or a freezing cold van and it never dropped a leaf. Check the leaves underneath for aphids but even when my tree was infested (I babysat a neighbor's plants!) it still didn't drop its leaves. Stick your finger in the soil about 2" and if dry, water well. Then don't water again for a week. If soil still damp, wait about three more days and repeat feeling the soil. After a while, you will know what your tree likes. That schedule may have to be adjusted a bit depending on the Season as it will need more frequent watering, perhaps, in the Summer. If the soil is really old, tip the tree over on its side, gently remove as much as possible and give it some new soil.

sometimes leaves will drop if the plant has recently been moved. Needs time to acclimate to new location. Also overwatering might be the problem.